37 HP is about 12 high for a really good running KDX,even with a pipe/porting/head mods 25hp would be pushing it.
Im pretty sure 18/20 hp is what they have stock. They arent fast but make great little woods bikes,just gotta buzz em and row the gears to make em move well.
A KTM200 might approach 35 hp at max buzz and weighs less and less the newer it is.
Google KDX info and some kind of power output will pop up somewhere.
Some bikes around at times